During seismic exploration operations, a seismic signal is propagated into the earth. Reflections of the signal which occur at the interface of geological layers may be sensed by seismic sensors, such as geophones or hydrophones, and recorded. Information about the underlying geological layers may then be derived from the recordings.
The type of seismic sensor used in a particular exploration operation has depended, in large part, on the location where the sensor may be deployed. In addition to selecting from the well known geophone and hydrophone categories, sub-categories exist within each type of sensor family. For example, geophones are often provided in two configurations which pertain to the manner in which one or more cables are connected to each geophone within a geophone string. In marsh type geophone strings, where a portion of each geophone may be penetrated into the ground with a specialized driving tool to improve the ability of the geophone to sense the reflected seismic signal, the cable is preferably connected in an axial or vertical alignment with the geophone to allow for the tool to more easily engage the geophone. In contrast, for dry land type geophone strings, in which each geophone may be pushed fully or partially into the ground or sit directly on the ground surface, the preferred alignment of the cable with each geophone has been a radial or horizontal alignment in order to reduce or minimize the portion of the cable above the ground surface exposed to the wind and thereby inhibit the creation of potentially error inducing wind noise in the sensor. As may be appreciated from the preceding discussion, the use of different geophone strings for each of these purposes tends to increase inventory costs and logistic complexity.
The above-described differentiation between the various types of geophones has been accompanied, somewhat ironically, by an increased capacity of the various sensing technologies. For example, in the past, the particle sensing capability of geophones has in some cases been provided by relatively bulky gyroscope-based accelerometers. By way of contrast, today, this same capability may be provided, for example, by relatively small MEMS based accelerometers. The miniaturization associated with MEMS sensing technologies and the associated reduction in costs has naturally led to the development and increased use of so-called multi-component type seismic sensors, e.g., sensors which incorporate technologies associated with both geophones and hydrophones. Indeed, today's seismic sensors may incorporate not only both geophone and hydrophone type sensors but also sensors for detecting other types of reflected signals and/or characteristics of the various environments in which the sensor may be used.
With regard again specifically to geophones, some have proposed to use the same geophone in diverse environments by fixing the position of the cable at an angle between the vertical and the horizontal, see e.g., U.S. Pat. No. 8,000,171. Such solutions have been found unacceptable for reasons including that a tension must be applied and maintained to the cable exteriorly of the seismic sensor in order to achieve a desired vertical or horizontal orientation thereof. Among other problems, this tension may induce a torque or other force on the sensor after the sensor has been set thereby causing the sensor to become displaced from its set position or worse, fully decoupled from the ground. The risk of this occurrence is particularly acute if the integrity of the ground is compromised by the presence of mud and/or snow. Moreover, this problem may be further exacerbated by the continued development of multicomponent seismic sensors having less mass and less volume than ever before. These seismic sensors may be even more prone to inadvertent displacement caused by cable tension forces of even a relatively small magnitude. Conversely, cable tension in the cable may actually force the cable to be maintained in a set position. However, over time, the tension in the cable may dissipate, and without this stabilizing force, the sensor may be displaced from a desired set position.
What is needed then is a cable management solution which allows the seismic sensors of today, and tomorrow, to be re-used in different environments or configurations and which can maintain an angle relative to the cable to which it is connected without the application of undue tension thereto.